General manager Brian Sabean said the Giants were motivated to execute the trade by a lack of progress from Matt Cain, who was placed on the disabled list July 21 with elbow inflammation. Sabean said Cain has not responded to "the protocols that our orthopedic people are checking on" and will likely require further opinions, with no timeline for his potential return.

"There may be a worst-case scenario behind the scenes -- we haven’t got to that," Sabean said. "But the impetus to act as quickly as we did (was) we really felt that he’ll be out for a while no matter what, and we didn’t want to stay constant."

Peavy, who will make his Giants debut Sunday against the Los Angeles Dodgers, is 1-9 with a 4.72 ERA this season with the Red Sox. But the Giants feel he’s an upgrade over Yusmeiro Petit, the long reliever who has been filling in for Cain. Sabean said the deal was also accelerated by Boston’s willingness to buy out most of Peavy’s remaining contract, leaving the Giants responsible for just $2 million for the rest of this season.

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That was key for Sabean as he continues to search for potential position player upgrades before the July 31 trade deadline, particularly at second base, where the Giants have been hit hard by injuries and on Friday called up Dan Uggla days after signing him to a minor-league deal. Sabean said Saturday that while Peavy’s deal leaves the Giants with some financial flexibility, "There just aren’t enough players on the table at this point."

Peavy, 33, will be reunited with manager Bruce Bochy, for whom he pitched with the San Diego Padres from 2002 until 2006, when Bochy left to manage the Giants. He returns to the National League for the first time since 2009; Peavy won the N.L. Cy Young Award in 2007 and was a two-time All-Star with the Padres.

Despite his record this season, Sabean said the Giants had eight different scouts watch Peavy pitch in recent months, and had all eight "recommend him as a fourth starter and recommend we trade for him."

"He doesn’t throw quite as hard (as in San Diego), but he’s still 92 mph, in that area, has a good breaking ball, changeup, and has that fire -- that’s the most important part," Bochy said. "He’s as tough a competitor as any pitcher or player I’ve ever had. That’s how hard he goes for you."

Escobar and Hembree were both touted prospects in the Giants’ system, but Sabean said they had fallen recently on the organization’s internal prospect rankings, as evidenced by other pitchers (Petit in Escobar’s case and George Kontos, among others, in Hembree’s) being promoted to the majors ahead of them in times of need this season.

"Both these guys, in our estimation, needed more time in the big leagues," Sabean said. "But they’re major-league pitchers."

Finally, Sabean was asked whether he expects Cain to pitch again this season. His answer was noncommittal.

"I’m not a doctor. That’s out of my realm," Sabean said. "I go with the medical team. We haven’t checked off all the boxes, so I can’t answer that, I really can’t."

The Giants today also placed catcher Hector Sanchez on the 7-day concussion DL and called up Andrew Susac from Triple-A Fresno. Sanchez suffered a concussion when he was struck by a foul tip Friday night. Susac, the Roseville native and Jesuit High alum, learned he was being called up late Friday and arrived at AT&T Park this afternoon.

"It’s a dream come true," Susac said, standing behind the backstop after batting practice today. "I didn’t know if it would come this early, but it’s here and it hasn’t really kicked in yet. Just trying to soak it in."

* One more note from Sabean’s press conference: The general manager mentioned that both Escobar and Hembree were deemed expendable as they were not part of the Giants’ "no-trade list."

Sabean didn’t get into specifics about the no-trade list, but did say that the Giants have fielded trade interest from different teams about "15 different pitching names … so that’ll tell you how deep" their pitching is in the minors.

* Sabean was also asked if he sees Peavy in a Giants uniform in 2015 and said that hasn’t been part of the discussion yet.

"We’ll cross that bridge," he said, adding that an option in Peavy’s contract for 2015 will not kick in because it’s predicated on Peavy reaching a certain number of innings. "We’re just worried about today, this year."

* Peavy was due to arrive in San Francisco this evening, and will likely be available to the media after tonight’s game. For now, the Giants turn their attention to trying to figure out Kershaw, who’s 11-2 with a 1.92 ERA and whose career success against the Giants needs little reminding.

But here it is anyway: In 23 career games against the Giants, Kershaw is 11-5 with a 1.48 ERA. And at AT&T Park, he is 6-2 lifetime with a 0.78 ERA. First pitch, minutes away.

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